BIG UPDATE: Our pick to control your monitor just got better

Headaches. Dry and itchy eyes. Blurred vision, sore shoulders, muscle spasms and involuntary twitches. All of these are symptoms of digital eye strain caused by hours of staring at screens. It's no secret that technology causes some unique health problems, but what isalarming is the scale.

In fact, a survey found that 90 percent of Americans look at digital screens - a computer, smartphone or tablet - for more than two hours per day. Nearly 60 percent of those people use their devices for more than five hours per day, with 70 percent of them using two or more of their devices at the same time.

That's certainly a lot of screen time. What are the consequences? More than 65 percent of Americans have had symptoms of digital eye strain, including neck, shoulder and back pain, headaches, blurred vision and dry eyes.

Surprisingly, 27 percent of Americans don't know that you can prevent symptoms by wearing special glasses designed to protect against digital eye strain or cutting back on your screen time.

There's also this free download that I use personally and with its latest update, it just got a whole lot better.

F.lux Version 4

It's called f.lux and it automatically adjusts your monitor's color temperature at nighttime. It shifts your monitor to a red tint, which is less disruptive to your sleep pattern.

F.lux automatically detects your geographic location and will begin adjusting your display to your time zone. Note: You can change your location to match your schedule. Just click on Settings.

If you need precise colors while you edit photos or do other color-sensitive tasks, you can disable f.lux. Or, if you want to watch a movie and have the colors look right, you can put f.lux in Movie Mode. This disables f.lux for two and half hours.

Note: If you first install and run f.lux at night, your monitor will suddenly take on a serious shade of red. Give yourself a little time to get used to it. If the colors still don't seem right, you can adjust the warmth setting to what's most pleasing to your eyes.

New updates

If you're already using f.lux, you'll be ecstatic to know that its new recent update just made an excellent program even better.

First, with version 4, f.lux's developers improved the software's performance with games.

There's also a new "Bedtime Mode" that's even warmer than before to get you ready to sleep.

With f.lux version 4, users can also disable f.lux on specific apps, such as Photoshop and video players.

Other great improvements:

predictions of how light affects your body

a backward clock to remind you not to stay up late

color filters to prevent eyestrain

a wider range of color settings

New hotkeys for adjusting color ("Alt+Shift+PgUp" and "Alt+Shift+PgDn")

With all these great new features, f.lux version 4's improvements are definitely worth the upgrade.

Download instructions

Click on one of the blue links below or proceed to this link. Click on the blue tab Download f.lux. Open the Windows .exe file (or .app file on a Mac), when it's installed, you should see f.lux's control panel. Adjust your daytime/sunset/bedtime settings accordingly. The screen effect should be instantly noticeable. To revert back to your original settings, just quit f.lux.